This invention is related generally to the delivery of drugs to a patient and, more particularly, to the intracranial delivery of drugs.
The introduction of drugs or other therapeutic agents to sites in the brain is common in many neurosurgical procedures today. Such procedures include the delivery of chemotherapeutic agents such as protein toxins to brain tumors, delivery of genes used in genetic therapy, and the delivery of neural cell or tissue during transplantation surgeries. One area in which use of such procedures is particularly relevant is in drug delivery for treatment of epilepsy and other movement disorders.
In the last twenty years, major advances have been made concerning the identification of specific epileptic syndromes which respond poorly to treatment by ingested drugs but may be successful treated by surgical intervention. Recent advances in diagnostic technology and surgical techniques have led to an increasing use of surgical treatment of epilepsy. In addition, through the discovery that particular seizures result from particular neuronal activity, the targeting of the causal neuronal activity for treatment by anti-epileptic drugs has achieved success. The neuronal cell populations responsible for such activity may be eliminated through the direct delivery of drugs such as excitotoxins. The elimination of specific epileptic disturbances has allowed people afflicted with epilepsy to be relieved of disabling seizures and the disturbing side-effects of treatment while avoiding the long-term psychosocial consequences of living with an uncontrolled epileptic disorder.
There are several prior art apparatuses which allow for the introduction of drugs or therapeutic agents to selected brain tissue. One such apparatus is disclosed in U.S. Pat. No. 5,554,148. This patent involves a refillable neural implant which attempts to provide a continuous supply of drugs or other factors to the brain and other tissues at a controlled rate. Such a continuous supply is intended to compensate for deficits in secretions by the patient""s improperly functioning source cells. The disclosed device requires the permanent or long-term presence within the brain of the cell chamber which receives and disperses the drugs. Such a presence is not desirable if proper treatment can be achieved without it.
Another prior art device is described in U.S. Pat. No. 5,006,122 which discloses a brain tissue transplantation method utilizing a cannula within a cannula assembly. The first cannula is of the large bore type and is fixed to a stereotactic holding apparatus to allow for its insertion into the brain to the transplant site. The second cannula, which carries donor tissue and a stylet which is used to expel the tissue from the second cannula, is guided within the lumen of the first cannula to the transplant site. The tissue is then transplanted into the brain by withdrawing the first and second cannulas while the stylet within the second cannula is maintained in a fixed position. The stylet is later removed, leaving only the transplanted tissue in the patient.
The ""122 device does not provide for reliable delivery of small volumes of matter to a selected site in a patient. Small volumes of fluid injected from the ""122 instrument tend to adhere to the surface area of the cannula and flow up around the outside wall of the guide cannula.
U.S. Pat. No. 5,792,110 attempted to overcome this problem. It discloses a cannula within a cannula assembly for delivery of therapeutic agents within a patient""s brain. The assembly includes a rigid guide cannula for penetrating a selected site at a predetermined depth and a flexible delivery cannula for delivering the therapeutic agent at the site. The assembly attempts to overcome the problem of injected fluid flowing up the tract created by the insertion of the guide cannula by utilizing a delivery catheter having a much smaller diameter than the guide cannula. It is also disclosed that the delivery cannula is deflected by the guide cannula so that it enters brain tissue at a transverse angle with the guide cannula tract. While an improvement over the prior art, these methods of intracranially delivering therapeutic agents present additional problems, are not easy to use and do not fully prevent the flow of the agents out of the cannula tract.
Therefore, there is a continuing significant need in the field of intracranial drug delivery, particularly involving the introduction of cannulas or catheters into the interior of the brain, for improvements in accuracy and effectiveness of drug delivery, while retaining ease of use. An improved device achieving these goals would improve treatment of the disorders and diseases noted above.
It is an object of the invention to provide an improved intracranial drug delivery device which ensures delivery to the selected site.
Another object of the invention is to provide an intracranial drug delivery device which is simple in structure and operation in order to facilitate effective drug delivery.
Another object of the invention is to provide an intracranial drug delivery device which allows for precise drug delivery to selected brain tissue while avoiding extensive trauma to and scarring of brain tissue.
Another object of the invention is to provide an intracranial drug delivery device including a guide catheter having an inflatable balloon to seal or occlude the tract created during insertion into the brain.
Another object of the invention to provide a method of accurately delivering a drug to selected tissue in a patient""s brain which minimizes injury to the brain.
Still another object of the invention is to provide a method of safely delivering a drug to selected tissue in a patient""s brain through use of an assembly including two catheters.
Yet another object of the invention is to provide a method of ensuring delivery of a drug to a selected site in a patient""s brain through use of a guide catheter having an inflatable balloon to seal the catheter tract.
These and other objects of the invention will be apparent from the following descriptions and from the drawings.
This invention is an improved assembly for effectively delivering a drug to a patient""s brain and methods of use thereof. The invention represents a significant advance over the state of the art by providing novel elements, including an inflatable balloon which is able to seal or occlude the catheter tract without damaging the surrounding brain tissue.
The assembly includes a guide catheter and delivery catheter which cooperate to allow for precise drug delivery. The guide catheter has proximal and distal ends, proximal and distal openings and a passageway which extends from one opening to the other. It also includes at least one lumen which extends from the proximal end to the distal end where it terminates at and is in communication with an inflatable balloon.
The delivery cannula is receivable within the passageway of the guide cannula through the proximal end so that it may be guided to the selected site for drug delivery. The delivery catheter has a first opening at its first end and at least one second opening at its second end. The second opening is preferably positioned within the brain adjacent to or near the selected site. An axial bore extends between the first and second opening and provides a path for the drug to reach the selected site in the patient""s brain.
The balloon is inflated to seal or occlude the catheter tract, thereby preventing the drug from leaking or xe2x80x9cbackflowingxe2x80x9d away from the selected site. This enables the drug to be fully absorbed by the brain tissue at the selected site to permit proper medical treatment. The balloon is located on the outside of the guide cannula and is separated from the passageway so that it does not protrude into the passageway during inflation. The balloon is preferably deflatable to enable removal of the assembly from the brain after drug delivery to the selected site.
In a preferred embodiment, the second opening of the delivery catheter extends beyond the distal opening of the guide catheter when the delivery catheter is inserted into the passageway. The passageway is preferably slightly larger than the delivery catheter to facilitate insertion of the delivery catheter into the passageway. It is also preferred that the second opening is coaxial with the bore.
An alternative embodiment provides that the second opening of the delivery catheter include multiple openings for delivering the drug to the selected site. These openings need not be coaxial with the bore.
The assembly preferably includes a stylet which is receivable within the passageway for use during insertion of the guide catheter into the brain. The stylet is preferably rigid to allow for precise positioning of the guide catheter inside the brain.
The preferable delivery catheter includes a hub at its first end to facilitate movement of the delivery catheter with respect to the guide catheter.
The invention also includes a method of using the inventive assembly to deliver a drug to a selected site in a patient""s brain. The method comprises: inserting into the brain the guide catheter such that the distal opening is near or just short of the selected site; inflating the balloon therein by injecting air through the lumen so that a tract created by the insertion of the guide catheter into the brain is sealed; inserting into the passageway through the proximal opening a delivery catheter; administering the drug to brain tissue at the selected site by passing the drug through the bore; deflating the balloon; removing the delivery catheter from the brain; and withdrawing the guide catheter from the brain.
It is preferable that a stylet is positioned within the passageway during insertion of the guide catheter into the brain and that the stylet is removed from the passageway through the proximal opening before the delivery catheter is inserted.
In one embodiment of the inventive method magnetic resonance imaging (MRI) is preferably utilized to aid the placement of the guide catheter in the brain. Therefore, in this embodiment it is preferred that the stylet be of MRI compatible material such as tungsten.
It is also preferred that the second opening of the delivery catheter extend beyond the distal opening after the delivery catheter is inserted into the guide catheter so that it is adjacent the selected site. It is further preferred that the delivery catheter and guide catheter are removed from the brain simultaneously. Furthermore, the deflating step is preferably performed after the drug has been substantially absorbed by brain tissue at the selected site.
In the preferred embodiment, the balloon is inflated before the delivery cannula is inserted into the passageway. In an alternate embodiment, the balloon is inflated after the delivery cannula is inserted into the passageway.
Another method of use of the inventive assembly to ensure effective drug delivery at a selected site in a patient""s brain comprises: preparing for insertion into the brain the guide catheter; positioning in the passageway a stylet to prevent brain matter from entering the passageway upon insertion of the guide catheter into the brain; inserting into the brain the guide catheter and stylet; removing the stylet from the passageway; inflating the balloon by injecting air through the lumen so that a tract created by the insertion of the guide catheter into the brain is occluded; inserting into the passageway the delivery catheter; administering the drug to brain tissue at the selected site by passing the drug through the bore; deflating the balloon after the drug is substantially absorbed by the brain tissue at the selected site; removing the delivery catheter from the brain; and withdrawing the guide catheter from the brain.